Airplane



Dec. 11, 1945. T. H. HUFF 2,390,939

' AIRPLANE Filed Aug. 15, 1958 7 Sheets-Sheet 1 T. H. HUFF Dec. 11, 1945.

AIRPLANE 7 Sheets-Sheet 2 Filed Aug. 13, 1938 T. H. HUFF AIRPLANE Dec. 11, 1945.

Filed Aug. 13, 1938 '7 Sheets-Sheet 5 T. H. HUFF Dec. 11, 1945.

AIRPLANE Filed Aug. 13, 1938 7 Sheets-Sheet 4 T. H. HUFF Dec. 11, 1945.

AIRPLANE Filed Aug. 13, 1938 '7 Sheets-Sheet 5 .T. H. HUFF Dec. 11, 1945.

AIRPLANE Filed Aug. 13, 1938 7 Sheets-Sheet 6 T. H. HUFF Dec. 11, 1945.

AIRPLANE Filed Aug. 13, 1958 '7 Sheets-Sheet 7 Patented Dec. 11, 1945 STATES PATENT OFFICE 44 Claims.

This invention relates to certain improvements in airplanes and more particularly to an airplane of a tailless type; and the nature and objects of .the invention will be readily recognized and understood by those skilled in the aeronautical art in the light of the following explanation and detailed description of the accompanying drawings illustrating what I at present believe to be the preferred embodiments or aerodynamic, mechanical and structural expressions of my invention from among various other embodiments, forms, designs, arrangements, constructions and combinations of which my invention is capable within the broad spirit and scope thereof.

My present invention relates to the design of airplanes of the so-called tailless types and is directed to overcoming the problems and reducing the diiiiculties inherent in and encountered with such types. The invention is fundamentally concerned with the design of an airplane of such type that is truly tailless, that is. one in which there is no aerodynamic structure substantially to the rear of the lifting surface of the airplane and no aerodynamic structure substantially forward of such lifting surface, whether such surface be in the form of a monoplane wing or multiplane wings, so that all aerodynamic structures or elements are substantially disposed within the projected area or plan of the lifting surface and/or above or below such lifting surface. With the prevailing types of socalled tailless airplanes, various expedients, such as sweep back and staggered relation of vertically spaced multiplane wings are resorted to as substitutes for the rearwardly located tail of the conventional types of airplane, but, in a taill ss design of the present invention, no such expedients are present as no substantial sweepback or stagger of the wing or Wings is utilized so that the design embodies a wingor wings having the maior longitudinal or spanwise axes at substantially or approximately right angles or perpendicular to the fore and aft or longitudinal axis of the airplane.

The problems of longitudinal stability and longitudinal control of thetailless types of airplane, are fundamental ones inherent in the general type and these problems ar met with in anaccentuated and high degree in a tailless airplane of the type characterized by the basic design of my invention in which design such means as sweep back or stagger of the wing or wings, or other means are substantally eliminated. The basis for obtaining longitudinal difliculties.

stability in a tailless airplane embodying my fundamental design, is provided by employing a lifting surface in the form of a wing or wings having an inherently longitudinally stable airfoil section, that is, a section that provides a substantial positive moment about the aerodynamic center at zero (0) lift, so that such lifting surface has a center of pressure movement in the proper directions relative to changes in the angle of attack of the lifting surface to thereby provide for the required inherent longitudinal stability throughout the flight range.

The shifting or changing of the location of the center of gravity of a tailless airplane due to the shift in weight distribution by changes in useful load is another problem inherent in the type and one that is rendered of increased importance by the present airplane of my design embodying an inherently longitudinally stable lifting surface or wing, because in a tailless airplane, incorporating such an inherently longitudinallystable wing, the practical location for the center of gravity of the airplane is within definite definable limits that are of considerably smaller range than those encountered in more conventional tailless or tailed types of airplanes. A further feature and characteristic of my present invention resides in the design of the airplane to provide such a structural and aerodynamic relationship between the longitudinally stable lifting surface or wing or wings and the other elements of the airplane, with the weight distribution and possible useful load location changes, that a predeterminedbut definite limited range of center of gravity location is provided for while maintaining stability and controllability within practical flight limits, and in such a manner that the center of gravitymay not shift or change beyond the limitation of the said predetermined range.

Another feature of the invention in relation to changes in center of gravity location of the tailless type of airplane hereof, is found in the provision for selectively adjustably trimming the airplane longitudinally in order to compensate for changes in the center of gravity location to relieve theload on the pilot's controls that would otherwise be present.

The longitudinal controllability throughout the flight range of an airplane of the tailless type, particularly when of the truly tailless type such as provided by my present design, includes certain aerodynamic and structural problems and One of such problems anddifficul- U a ises from the requirement of the design for location of all aerodynamic elements or members substantially within the plan or projected area of the lifting surface or wins, so that, whatever movable longitudinal or pitching control surfaces may be employed, such surfaces mustbe located substantially within the plan or projected area, and/or above or below, of the wing and preferably, although not necessarily, to the rear of the center of gravity of the airplane. with a longitudinal control surface or surfaces so located, the longitudinal or pitching control substantially within the plan or projected area of and/or above or below the wing, results, upon initiation of the control movement of such a longitudinal control surface, in the creation of longitudinal control forces acting a short distance away from the center of gravity of the airplane and in directions that cause the airplane to be displaced in the direction opposite to that desired. This first movement resulting from such initially produced vertical control forces, is then followed by pitching movement of the airplane in the direction desired in accordance with the longitudinal control moments developed by the displacement of the longitudinal control surface. This hunting or adverse displacement of the airplane is a very undesirable flight condition and particularly objectionable in the handling and piloting of a tailless airplane.

The practical elimination or substantial reduction of the foregoing tailless airplane longitudinal control problems is a feature of my invention and is characterized by the provision of one form of longitudinal control system of the invention that includes a vertically displaceable longitudinal control, surface or surfaces substantially within the projected area or plan of the wing or lifting surface for developing the required pitching moments acting in the desired directions, together with means in the form of a vertically displaceable surface substantially within the projected area of the wing for displacement in such relation to any particular direction and degree of displacement of the iongitudinal control surface, as to neutralize or substantially eliminate or reduce the adverse vertical control forces developed by the displacement of the longitudinal control surface, so as tethereby reduce the undesirable conditions above pointed out as inherent in such longitudinal control of a tailless airplane of the types referred to herein.

I have discovered and determined that the neutralization or reduction in the undesirable adverse vertical control forces developed by vertical displacement of the longitudinal control surface or surfaces, by the use of another vertically displaceable surface or surfaces, requires a varying relative angular relation between a control surface and such a force neutralizing surface, which relationship basically requires displacement of the neutralizing surface in the opposite direction from that in which the control surface is displaced; and further that the ratio or relation between the opposite angles at which these movable surfaces are respectively displaced relative to the wing or lifting surface, varies in accordance with other flight conditions, such as the angle of attack of the wing or lifting surface and the direction of displacement of the longitudinal control surface, that is, whether such latter surface is displaced to a positive or negative angle relative to the lifting surface.

Another feature of my invention is the provision of a design and arrangement of longitudinal control system functioning in accordance with the foregoing principles and by which the varying relation between the angular displacements of a longitudinal control surface and a vertical control force neutralizing surface may be obtained as required in accordance with and under the varying flight conditions, through the medium of adjustment of the angular displacement and direction of displacement of the neutralizing surface relative to the angular displacement and direction of displacement of the longitudinal control surface.

My invention further provides in the practical applications and adaptations of the basic longiadjustable relative to the control surface, or, in

tudinal control principles of the foregoing form of longitudinal control of my invention, for either mounting a vertically displaceable longitudinal control surface on and carried by a vertically displaceable vertical control force neutralizing surface, with the latter surface independently independently mounting the longitudinal control surface and the neutralizing surface on the wing, with the latter surface displaceable or adjustable to determine its angle of displacement and direction of displacement relative to that of the control surface independently of displacement of the control surface; and, as a further feature in providing, if desired, for utilizing such neutralizing surfaces as ailerons or roll control surfaces without interfering with their operation as neutralizing surfaces per se.

In accordance with a further feature of the invention, in connection with those forms of the longitudinal control that embody a displaceable longitudinal control surface and a vertically displaceable control force neutralizing surface, these surfaces are coincidentally, but diiferentially op-.

erated for longitudinalcontrol by a suitable control operating mechanism, but when such surfaces are so coincidentally and differentially operated, the forces acting upon the pilot's control are reversed and therefore, following a further feature and characteristic of the invention, a form of irreversable control mechanism or some other form of mechanical and/or aerodynamical means for reversing. the forces on the pilot's control is utilized.

The longitudinal control, following a further featureof the invention, may be provided by vertically disposed Eterally displaceable control surfaces mounted at oradjacent the opposite wing tips and located above and below the wing, respectively, with the opposite surfaces above the wing operable independently of the opposite surfaces below the wing, together with suitable control operating mechanism for selectively simultaneously laterally displacing in the opposite directions, either the control surfaces above the wing or the control surfaces below the wing, in order, in the former case, to establish stalling moments, and, in the latter case, diving moments, for the purpose of longitudinally controlling the aaeopse airplane. This form of, control likewise aflects to that desired and therefore, it is desirable to have some form of vertical control force neutralizing surface or surfaces which can be oper-.

ated in any suitable manner to aerodynamically cooperate with the longitudinal control surfaces in order to eliminate or reduce such adverse forces.

Another feature of the invention resides in the design and arrangement of directional or yaw control for airplanes of the tailless types, and particularly the truly tailless type of the basic design of my present invention; and this feature is characterized fundamentally by the provision of opposite wing tip rudders located substantially within the plan or projected area of the lifting surface or wing and laterally displaceable about vertical axes, together with an operating control system that provides for selective displacement of either wing tip rudder alone without displacement of the opposite rudder for directional or yaw control; and resides further in the provision for the design and location of such rudder surfaces so that upon operation of either of them, the displaced rudder surface functions primarily to establish drag at its respective wing ti-p with-s out causing any appreciable change in lift on the wing even with the displacement of the rudder establishing a stalling momentat such wing tip.

In connection with the directional control provided by the wing mounted rudders, the invention is characterized by the elimination of any fixed vertical fin surface as a part of the rudder and as distinguished from tip loss shields or surfaces or other remotely mounted fixed vertical surfaces for directional stability; and is further featured by the design of a rudder surface to tured by an arrangement which provides the forward ground engaging elements as spaced apart laterally and mounted for vertical displacement under landing and taxiing loads and forces, but which forward elements are so operatively associated with each other and with a common shock absorbing unit that vertical displacement of one element is necessarily accompanied by positive corresponding vertical displacement in the same direction of the other elements and independent vertical displacement of such ground engaging elements is thereby prevented, so that the airplane tends to always maintain its normal horizontal attitude laterally. 7

As a further feature of this invention, the design and arrangement of the landing gear provides for inherent directional stability while moving forward on the ground, due to the location of the center of gravity intermediate the forward and rear ground engaging elements with the rear element or elements normally directionally fixed and the forward element or elements of the landing gear mounted for castering so that upon ground contact in landing or in taxiing the airplane supported by such landing gear will always assume and maintain its direction of tially to the rear or forward of the lifting surface or wing, due to the practical impossibility of developing moments acting about the center of gravity of the airplane in order to change the ground supported attitude thereof and place the wing or wings or lifting surface at a suflicient provide a cambered section having the side of I greatest camber positioned inboard,

A further feature of the invention resides in the elimination of the directional or yaw control surfaces and the utilization of the ailerons or roll control surfaces for the dual function of roll control and directional or yaw control, thereby providing for flight operation of the tailless airplane of my basic design by only two controls.

The design, arrangement and mounting of a landing gear for a tailless type of airplane presents certain problems and difdculties due to the limitations on location imposed by the tailless design and especially by a design of the truly tailless type such as disclosed herein where it is desirable to avoid locating any structure appreciably outside of the plan or projected area of the lifting surface. An important feature of my invention is presented by a design. arrangement and mounting of a landing gear primarily adapted to the conditions met with in the truly tailless type of airplane hereof but which is of general application to other aircraft as well, in which landing gear the rear landingsurface engaging element or elements is located within the projected plan or area of the wing while the forward landing surface engaging elements are located spaced at minimum distance forwardly from the leading edge of the wing, and which rear and forward landing surface engaging elements so positioned have a definite location relative to the center of gravity of the airplane and the r nge of center of gravity movement, which location is referably equidistant from the center of gravity so that any tendency of the airplane to nose over backward is substantially eliminated.

The landing gear of the invention is also feaangle of attack to develop a lift coeflicient of a magnitude required for taking the airplane off. Thus, the angle of attack of the lifting surface or wing can not be sufficiently increased for take on and it either becomes impossible at the ground supported attitude of the airplane to acquire sufficient speed to develop the required lift from the wing at its angle of. incidence for the ground supported position of the airplane, or, an exces sively long ground run is required in order to attain the necessary speed to develop the required take off lift;

An important feature of my invention is directed to the elimination of the take off difficulties encountered with the taillesstypes of airthis thrust is above the center of gravity, such that as the thrust force is applied for take off, a moment is established acting around the center of gravity tending to nose the airplane down, but as forward speed increases, the lift developed by the wing is increased, and due to the fact that the wing is inherently longitudinally stable, this lift acts upwardly and forward of the center of gravity producing a stalling moment at small angles of attack which counteracts the thrust moment so that the load on the forward ele-' and the angle of attack increased up to that angle at which the lift force on the wing coincides with the center of gravity. Due to the fact that this coincidence may occur at an angle of attack less than that desired for take off, it is necessary to incorporate some additional mechanical means of increasing the angle of attack still further; and a further characteristic of this feature of the invention resides in providing a constantly acting upward force or forces of a, required magnitude tending to raise the forward portion of the body and wing of the airplane relative to the forward ground engaging elements of the landing gear in a manner to increase the angle of attack of the wing to such an angle that the required lift for take off may be developed.

Another feature of the invention resides in the provision of drag creating members to func tion as air brakes and in providing such members in a definite relation and association with the wing and the contour lines of opposite sides of the body and the airflow to the propeller in order that such drag creating members may function without interfering with airflow past the body and to the propeller, while in fact tending to increase the efficiency of such flow and to decrease propeller noise; and further in providing such members of a design and a location on the wing such than when operated the members establish a stalling moment for landing.

Another feature of the invention resides in providing an improved and efficient pilot operated steering mechanism for the forward caster ing ground engaging elements or wheels of the landing gear.

The invention further provides as a feature thereof, for the efficient cooling of an aircooled motor located at the rear of the airplane and enclosed from the airflow; and this feature is characterized by an arrangement of cooling air ducts or passages leading from the forward end or nose of the body to the motor and discharging downwardly and rearwardly through the fairing or housing structure for a rear ground engaging element of the landing gear, whereby during flight a suction force is established at the discharge end and a positive pressure at the intake end of such passages to thereby circulate air rearwardly therethrough for cooling the motor.

A further feature of the invention in connection with such cooling system provides for the automatic operation from the motor of a fan or blower for circulating air through said passages when the airplane is on the ground either at rest or taxiing and for disengaging such fan or blower when the airplane leaves the ground.

With the foregoing general features, characteristics and results in'view, as well as certain others that will be readily recognized from the following description, my invention consists in certain novel features in design, arrangement, combination and construction of elements and parts, all as will be more fully and particularly referred to and specified hereinafter.

Referring to the. accompanying drawings in which similar reference characters refer to corresponding parts throughout the several figures: Fig. 1 is a view in top plan of a tailless airplane embodying the design and various features of my invention.

Fig. 2 is a view in front elevation of the air-' plane of Fig. 1.

Fig. 3 is a view in side elevation of the airplane of Figs. 1 and 2.

Fig. 4 is a transverse vertical section through the wing of the airplane of Fig. 1 showing the mounting and associated control mechanism for the adverse control lift neutralizing surface and the vertically displaceable longitudinal control surface pivotally mounted along the trailing edge thereof.

Fig. 5 is a detailed view in side elevation of the unit for reversing the motion applied to concentric control pedal shafts.

Fig. 6 is a rear end elevation of the reversing v unit of Fi 5.

Fig. '7 is a more or less schematic view in perspective of the operating mechanism for the longitudinal control surfaces and adverse lift neutralizing surfaces where the former surfaces are mounted on the neutralizing surfaces and the neutralizing surfaces are independently adjustable relative to the control surfaces.

Fig. 8 is a more or less schematic view in perspective' of the operating mechanisms for the iongitudinal control surfaces and adverse lift neutralizing surfaces where the latter surfaces are mounted on the wing independently of the longitudinal control surfaces and are also operable differentially as ailerons or roll control surfaces.

Fig. 9 is a detail view of a portion of a modified form of longitudinal control surface and neutralizing surface operating mechanism of the irreversible type in which such surfaces are coincidentally and differentially actuated.

Fig. 10 is a perspective view more or less diagrammatic showing the opposite wing tip rudders and their mounting, together with the operating control system therefor including the control pedals and showing in dotted lines a control position of the right wing tip rudder and the associated pedals.

Fig. 11 is a more or less diagrammatic view in perspective showing the opposite wings and the spaced laterally swingable air brake surfaces with the operating mechanism therefor.

Fig, 12 is a view in perspective showing the forward castering landing wheels of the landing gear and the vertically swingable supporting struts or legs therefor associated at their inner ends with the common shock absorbing unit and force exerting spring acting thereon, together with the operating mechanism for arbitrarily steering said forward castering landing wheels.

Fig. 13 is a view in side elevation more or less schematic showing the body of the airplane in outline and indicating the center of gravity location relative to the landing gear wheels, and further showing the arrangement of operating system for the forward and rear wheel brakes, and also showing more or less diagrammatically the mounting of the rear wheel of the landing gear and its associated shock absorbing unit.

Figs. 13A, 13B, 13C and 13D, are purely schematic views in outline indicating progressively the altitude of the airplane and the directions of the various forces acting thereon during certain period of take-off, from ground position with engine off, to the moment of take-off.

Fig. 14 is a view in side elevation of the airplane of Figs. 1 to 3 and showing the air circulating ducts or passages of the engine cooling system together with the engine driven fan or blower -for mechanically circulating air through such .-ducts or passages while on the ground, and a form of automatic means for disengaging the blower while the airplane is in the air.

Fig. 15 is a detail view-in front elevation showing the air duct or passage intake at the forward or pressure end of the body. I

Fig. 16 is a detail view partly in vertical section showing the construction and arrangement of means for circulating cooling air over an engine exhaust pipe.

Fig. 17 is a detail view in vertical section through a cable slack take up unit as employed in certain of the control operating systems of the invention.

Fig. 18 is a view in vertical section through the forward or front wheels and their vertically displaceable supporting legs or struts in operative connection with the common centrally located shock absorbing unit and force exerting spring.

Fig. 19 is a view similar to Fig. 18, but showing the force exerting spring, shock absorbing unit, and wheel struts in their positions with the airplane supported on the ground.

Fig. 20 is a perspective view, more or less diagrammatic, showing a form of longitudinal control and operating system therefor embodying vertical opposite wing tip mounted laterally displaceable control surfaces above and below the wings.

A truly tailless airplane embodying the basic design and various features of my invention is illustrated by way of'example and not in all respects of limitation, in the accompanying drawings, and while the various features of the invention are of particular utility and efiiciency in overcoming and reducing the problems and difllculties of the tailless types of airplanes, it is to be understood that certain features are not only adaptable to and useful with other types of tailless airplanes, but aircraft generally, and such general adaptability of any such features will be referred, to hereinafter in the detailed descriptions thereof.

The illustrated embodiment hereof of my basic design and arrangement of tailless airplane, referring now particularly to Figs. 1, 2 and 3 of the drawings, includes a body or fuselage B of streamline form and, in the example hereof, of enclosed cabin type providing the occupant space or compartment which includes preferably, although not necessarily, a side-by-side seating arrangement as indicated by one of such side-by-side seats S shown in Fig. 13 of the drawings. This body B may be of any suitable or desired construction and includes, referring now to Fig. 14 of the drawings, a suitable enclosed space or compartment therein to the rear of the occupant compartment for receiving and housing the engine E in the upper portion thereof for driving, in the present instance, a pusher propeller P.

The body B may, as in the example hereof, include and provide at its rear upper side, an upwardly projecting vertical fin forming structure F. At its lower rear side, the body B is provided with a depending housing or fairing H for the rear wheel ill of the landing gear and as an outlet for the engine cooling air. The upper vertical fin F and the depending housing'or fairing H therebelow provide vertical fin area contributing to directional stability of the airplane.

The body B is mounted upon and carried by a landing gear that includes the rear ground engaging element or wheel Ill located within the housing or fairing H, which rear wheel is disposed in the vertical plane of the longitudinal or fore and aft axis of the body B, and the forward landing wheels ll spaced apart laterally of the body and located and positioned at opposite sides thereof spaced outwardly a considerable distance example hereof, of monoplane form although obviously, the invention is not limited or restricted to the use of monoplane wings as it contemplates and includes various multiplane wing arrangements within the fundamental requirements of the invention if desired or found expedient.

Inherent longitudinal'stability In the example hereof, the opposite wings LW and RW include the inner or root ends thereof formed by the center section wing panel providing the opposite wing stubs RW' and LW' in accordance with more or less usual design and constructional practice, and the wings are mounted and fixed to the body in the example hereof at approximately zero (0) degrees dihedral. The wings RW and LW are disclosed in Fig. 2 of the drawings as at approximately ,zero

(0) degrees dihedral.

The wings RW and LW forming the lifting surface of the airplane are mounted in' position relative to the body B such that the trailing edges of the wings, in this instance, are at substantially right angles or perpendicular to the longitudinal axis of the body and are located substantially in line with the rear end of the body so that the wings or lifting surface have no substantial rearward projection beyond the tail end of the body, or the body has no substantial projection rearwardly beyond the trailing edges of the wing.

The lifting-surface or wings RW and LW are of inherently longitudinally stable type and are without any substantial sweep back in the present instance, and in accordance with the truly tailless design of the invention, the lifting surface should have no appreciable sweep back but should preferably have its major medial longitudinal or spanwise axis approximately ,at right angles or perpendicular to the fore and aft or longitudinal axis of the body B and the airplane, although it is to be here pointed out that a design of my invention may, if desired, include some degree of sweepback for the purpose of physically balancing the airplane, but not for the primary purpose of securing aerodynamic stability per se.

The supporting surface or wings RW and LW for the airplane are, in accordanceiwith a basic characteristic of the invention, of an airfoil section such that these wings are inherently longitudinally stable, that is, a wing section which provides a wing having a substantial positive moment about the aerodynamic center at zero (0) lift, that is, a wing section with a substantial positive value 01120.

in the particular example hereof, a slight distance to the rear of the forward wheels I I of the landing gear, as will be clear by reference to Figs. 2-

and 3 of the drawings in particular, although this is not an essential or critical factor in the design. It so happens that in the particular design illustrated, the leading edges of the wings RW and LW have an outward rearward inclination to provide the normal taper of a cantilever wing.

Lateral or roll control The lateral or roll control for the design of tailless airplane of Figs. 1 to 3 may be of any suitable or desired type but in this instance is disclosed as a more. or less conventional control embodying the opposite wing ailerons or angularly vertically displaceable surfaces A forming trailing portions of the wing or lifting surface and adapted for operation through a suitable control operating mechanism. The ailerons A are mounted for a distance along the outer or tip portion of the span of the wings RW and LW and an operating mechanism is provided, referring now to Fig. 8 of the drawings, which includes the usual pilot's control stick or other manually operable control member C mounted for lateral swinging or movement for aileron actuation and coupled by means of a torque tube ll for transmitting such lateral rocking of the control stick through the connected opposite push-pull tubes 15 and I6 to the opposite wing ailerons A. The outer end of push-pull rod I5 is connected with a bell crank H, which bell crank is coupled by a link lla with the adjacent aileron A, while the outer end of the push-pull rod I6 is coupled with a bell crank l8 mounted in the wing LW and coupled with the aileron A of such wing by a link l8a. This arrangement of operating mechanism for the opposite wing ailerons A, while onl shown in Fig. 8 of the drawings, is adapted for operating the opposite wing ailerons A of Figs. 7 and 9, in order to obtain the usual actuation of those ailerons for lateral or roll control. However, the invention is not concerned with the specific operating mechanism for the ailerons or other roll control surfaces.

Preferably, each of the ailerons or roll control surfaces A is provided with a suitable trimming tab or trailing surface a mounted thereon and vertically angularly adjustable relative to the aileron. Such a tab a is shown on an aileron A of Fig. 1 of the drawings.

Longitudinal-0r pitch control The longitudinal or pitch control of my invention, adapted particularly for the conditions presented by the tailless type of airplane, is disclosed in one form and adaptation thereof in Fig. '7 when considered in connection with Fig. 1 of the drawings. This longitudinal control embodies the hereinbefore referred to principles of my invention by which longitudinal control or pitching moments are developed acting about the center of gravity of the airplane for longitudinal or pitching control thereof, and provides for reducing or substantially eliminating the adverse vertical lift resulting from the actuation of the longitudinal control surfaces L. I

The longitudinal control surface or surfaces may be, as in the present example, in the form of vertically angularly displaceable trailing portions of the lifting surface or wings of the airplane, such as surface L providing the trailing portion of each of the wings RW and LW along the span thereof. Each of these longitudinal control surfaces L is vertically angularly displaceable by means of a suitable operating mechanism to positive or negative angles relative to the lifting surface or wing in order to establish the desired longitudinal control or pitching moment acting in the required direction about the center of gravity of the airplane. The opposite wing longitudinal control surfaces L are simultaneously displaced to obtain the required longitudinal control, and, as heretofore pointed out, the displacement of these control surfaces develops adverse lift so that if these control surfaces L are displaced downwardly to cause the airplane to dive, then, upon initiation of this control movement, the adverse lift established will cause the airplane to rise. In the same manner, as the longitudinal control surfaces L are upwardly displaced so as to cause the airplane to pitch about the center of gravity in the direction of stall, then the reverse action takes place and the airplane is caused to sink by the adverse lift.

In accordance with my invention, provision is made for reducing or neutralizing these adverse lifts, caused by operation of the longitudinal control surfaces L. In the present expression of this feature of my invention, I have provided adverse lift neutralizing surfaces V in the form of vertically angularly displaceable surfaces forming portions of the lifting surface or wings of the airplane and I have mounted one such surface V on each of the wings RW and LW disposed spanwise thereof, with each. surface V hinged along a hinge axis 20 (see Fig. 7) between its leading edge and the trailing edge portion of the fixed wing structure there-ahead.

In the form of the longitudinal control arrangement of Figs. 1 and 7, the longitudinal control surfaces L are mounted on and carried by the neutralizing surfaces V, respectively, each longitudinal control surface L being hinged along a hinge axis 2| to the trailing edge of a surface V so that the connected neutralizing surface V and longitudinal control surface L of each wing, form vertically displaceable trailing portions of the wing and in their normal neutral positions carry out and define ,the normal airfoil section and contour of the wing.

For longitudinal control, the adverse lift neutralizing surfaces V of the opposite wings are simultaneously vertically displaced independently of displacement of surfaces L, into angular positions relative to the wings at angles relative to the angle of vertical displacement of the said longitudinal control surfaces L, and in directions opposite the direction of displacement of such longitudinal control surfaces. Suitable mechanism is provided for simultaneously angularly vertically displacing the neutralizing surfaces V about their hinge axes 20 and independently of the displacement of the longitudinal control surfaces, so that the adverse lift neutralizing surfaces V may be adjustably displaced arbitrarily by the pilot.

A form of operating and control mechanism for the adverse lift neutralizing surfaces V is more or less diagrammatically disclosed in Fig. 'l

.of the drawings and embodies a shaft or rotatable member 22 mounted in suitable bearings 2211 with this shaft disposed intermediate the opposite wings RW and LW and transversely of and through the center section RW' and LW', and the body B. -This shaft 22 is provided with internally threaded axial bores at its opposite ends with the threads of these opposite end bores oppositely threaded, that is, one bore having a right-hand thread and the other a left-hand thread. A threaded rod 23 is provided extending axially into and engaged by the threaded bore at the right-hand end of shaft 22, and a similar crank 33 is connected to a longitudinal control threaded rod 24 extends axially into and engages thethreaded bore at the left-hand end of the shaft 22. The opposite end threads of the shaft bores and the threads of the opposite rods 23 and 24 are arranged so that upon rotation of shaft 22 in one direction, the rods 23 and 24, which are held against rotation, but which are free to move axially, are simultaneously moved into-the shaft, while upon rotation of the shaft in the opposite direction, these rods are simultaneously moved outwardly from the ends of the shaft.

A bell crank 23a is mounted within the wing RW forward of the neutralizing surface V of that wing, and one arm of this bell crank is connected by a link 25 with the outer end of rod23, there being a universal joint 25a connecting the inner end of link 25 with rod 23. The other arm of bell crank 23a is coupled with a depending undersurface horn 26 on surface V by a link 26a. In the left-hand wing LW, there is provided a bell crank 24a forward of the neutralizing surface V of that wing and one arm of this bell crank is connected with the outer end of rod 24 by a link 21 through a universal joint 21a. The other arm of the bell crank 24a is coupled with a depending horn 28 in surface V by a link 28a.

The arrangement of the opposite wing bell cranks 23a and 24a with the linkage coupling the surfaces V through these cranks to theopposite rods 23 and 24in the shaft 22 is such that upon rotation of shaft 22 in one direction, the rods 23 and 24 are simultaneously drawn inwardly to simultaneously raise or vertically angularly displace the opposite wing neutralizing surfaces V, while rotation of shaft 22 in the opposite direction will simultaneously force the opposite rods 23 and 24 outwardly from shaft 22 and thus simultaneously lower or angularly displace the opposite wing surfaces V downwardly.

A pilot controlled and operated mechanism is provided for selectively rotating shaft 22 in either direction in order'to raise or lower the adverse lift neutralizing surfaces V of the opposite wings RW and LW, and such mechanism may, as in the example hereof, take the form of a shaft 29 rotatable by a hand crank 30 and having fixed thereon a sprocket or gear 3|. A sprocket or gear 32 is fixed on shaft 22 and is operatively connected with the sprocket or gear 3| of operating shaft 29 by means of a suitable chain 33. The shaft 29, with its operating hand crank 30, is mounted at a suitable location in the body B readily accessible to the pilot, and a visual indicating mechanism may be included that embodies a rack 34 engaged by the gear or sprocket 3| and carrying an indicator pin or pointer 35 for actuation by rotation of gear 3| to indicate the direction and degree of vertical. I

displacement of the adverse lift neutralizing surfaces V. r

In the form and arrangement of longitudinal control of Fig. 7, in which the opposite longitudinal control surfaces L are mounted On and hinged to the opposite neutralizing surfaces V, respectively, along the hinge lines 2|, thev operating mechanism for the longitudinal control surfaces L is, of course, coupled with and actuated by the pilots control stick C. In this instance, such mechanism includes a vertically disposed lever 36 mounted on each wing RW and LW intermediate or between a neutralizing surface V and the forward portion of the wing structure for rocking about an axis 360, intermediate its ends coincident with the hinge axis 20 of each respectivesurface. V. The upper arm of each connected by a link 38a with an arm of a bell crank 38 mounted in wing LW forward of its aft rocking movement of the pilots control stick or angularly displaces the longitudinal control surface L rearwardly thereof 'by means of a link 36b. The lower arm of crank 33 of wing RW is connected with an arm of hell crank 31 mounted in the wing forward of surface V, by a link 31a, and the lower arm of lever 36 of wing LW is neutralizing surface V.

tion intermediate the wings RW and LW and has its opposite arms operatively connected with the opposite wing bell cranks 31 and 38 between push-pull rods 39a and 39b. The bell crank 33 is rocked by and fromlongitudinal or fore and C through the medium of a link or a push-pull rod 40 connecting the stick C with an arm of the bell crank 39. Thus, forward movement of the control stick C simultaneously lowers or down wardly angularly displaces the opposite longitudinal control surfaces L while rearward movement of the control stick C simultaneously raises surfaces L upwardly, the angular displacement upwardly or downwardly of these surfaces L taking place about the hinge axes 2| thereof along' the trailing edges of the opposite neu tralizing surfaces V.

The arrangement of the operating mechanism for the opposite longitudinal control surfaces L, with the levers 36 of such mechanism rocking about the hinge axes of the neutralizing surfaces V, respectively, upon which surfaces the longitudinal control surfaces are mounted in trailing position, enables vertical angular displacement of th longitudinal control surface independently of and without effecting displacement of the neutralizing surfaces, notwithstanding the positions to which such latter surfaces may have been adjusted.

The vertical displacement upwardly or down- I wardly of the adverse lift neutralizing surfaces V is accomplished by the operating mechanism therefor as heretofore described, by rotation of the hand crank 30 in the required direction to raise or lower th surfaces V, and such adjustment of surfaces V is carried out independently of the longitudinal control movements of the surfaces L by the fore and aft rocking movement of the control stick C. It is to be noted at this point that the operating mechanism for simultaneously vertically displacing the neutralizing surfaces V, is of the irreversable type provided by the threaded rods 23 and 24 engaged in the threaded shaft 22 so that this operating mechanism will maintain the neutralizing surfaces V in an angularly adjusted position against displacement and without requiring the application of any forces by the pilot to maintain the surfaces in their adjusted position.

In the flight operation of the longitudinal control surfaces L, and the adverse lift neutralizing surfaces V, in the particular design of tailless airplane here shown as an example, I have discovered and determined that there is a varying ratio throughout the flight range between the angle to the wing or lifting surface at which the longitudinal control surfaces L are displaced and the opposite angle at which the neutralizing surfaces V are displaced in order for the latter to neutralize or reduce the adverse lift developed by the displacement of the surfaces L. As hereinbefore pointed out, the surfaces V, in order to function to neutralize or reduce the adverse lift, must be displaced in a direction opposite the direction of displacement of the longitudinal control surfaces L, that is, when the longitudinal control surfaces are displaced to a positive angle as for a, dive, then the neutralizing surfaces are displaced to a negative angle, while if the longitudinal control surfaces are displaced to a negative angle to cause .the airplane to stall, then the neutralizing surfaces are displaced to a positive angle relative to the lifting surface.

The relationship between the angle of a neutralizing surface and the opposite angle of dis.- placement of a longitudinal control surface varies with the angle of attack of the lifting surface or wings of the airplane, and also, this relationship between the opposite angles of these surfaces varies in accordance with the direction of displacement of the longitudinal control surface,

-that is, as to whether the surface is displaced to a positive or negative angle. For example, at high angles of attack of the lifting surface or wings, in general, in. order to neutralize or compensate for adverse lift, it is necessary to dis-- place the neutralizing surfaces to larger angles, both positive and negative, than at low angles of attack, and in this high angle of attack condition, with the longitudinal control surfaces at negative angles, it is necessary to displace the neutralizing surfaces to slightly larger positive angles than when the control surfaces are at positive angles. At low angles of attack of the lifting surface or wings, I have found that the neutralizing surfaces may be moved to smaller positive than negative angles in order to neutralize or compensate for the adverse lift developed by the displacement of the longitudinal control surfaces to negative and positive angles, respectively. I have also determined in connection with .the above, that for the condition of no variation in the lift force, the moment is greater for positive angles of the longitudinal control surfaces, that is, for the dive condition, thanfor the negative angles of the longitudinal control surfaces, that is, for the stall condition. At low angles of attack of the lifting surface or wings with the lift force unchanged, the resulting moment is greater for the negative angles of displacement of the longitudinal control surfaces representing the stalling moment than the resulting moment is its: the corresponding positive angles of displacement representing the dive moment.

or variations in the weight distribution of the useful load. The adjustment of the neutralizing surfaces V for purposes of longitudinal trim, may be carried out independently of and without interfering with the longitudinal control operation of the surfaces L mounted on the neutralizing surfaces, such surfaces L, being operable in any position to which surfaces V are displaced or adjusted. Upon adjustment of the neutralizing surfaces V to a displaced position, for longitudinal trim, these surfaces may then be operated from the adjusted position for purposes of neutralizing adverse lift.

Longitudinal trim may also be obtained by a lifting surface or wing camber varying operation of the longitudinal control surfaces and the neutralizing surfaces, with those forms of the invention in which the longitudinal control surfaces are mounted on and carried by the neutralizing surfaces, through displacement of the longitudinal control surfaces and the neutralizing surfaces in thesame direction. For example, with the longitudinal control system and arrangement of Fig. '7, by displacing the neutralizing surfaces V and longitudinal control surfaces L in the same direction, the camber of that portion of the span of the wing occupied by such surfaces is changed and the airplane may be trimmed longitudinally by such camber change. After such a, wing camber varying displacement of the longitudinal control surfaces and the neutralizing surfaces,

' with the arrangement of Fig. 7, the operation of the longitudinal control surfaces the cooperative independent displacement of the neutralizing surfaces, as hereinbefore explained, may then be carried out for longitudinally controlling: the

airplane.

Attention is here directed to the fact that in the the selection of an inherently longitudinally stable wing, there is available a large selection of ranges of center of gravity location.

For example, with such inherently longitudinally stable wings having a positive Cmo moment, that is, a moment having a value of from 0 to +.020, there is available a very large degree of controllability within the flight range due to the small inherent stabilizing moments. 1

Nevertheless, it is a fact that in order to main tain stabili y in the flight range, the location of With the independently operable adverse lift neutralizing surfaces V of the arrangement of Fig. 7, the pilot, upon displacement of the longitudinal control surface L for longitudinal control,

may then, by rotation of the hand crank 30 in I the proper direction, displace the neutralizing surfaces in a direction opposite to that of the displacement of the longitudinal control surfaces and at a relative angle that may be required in order to neutralize the adverse lift developed by the displacement of the longitudinal control surfaces. This independent operation and adjustment of the neutralizing surfaces thus enables the pilot to displace and adjust such surfaces in accordance with the flight conditions, including angle of attack of the lifting surface or wings and direction and degree of displacement of the longitudinal control surfaces. 7

These vertically angularly displaceable adverse lift neutralizing surfaces'V and the irreversible operating mechanism therefor, may be utilized for the purpose of longitudinally trim ming the airplane to compensate for changes in the center of gravity location resulting from shifts the center of gravity is limited to a range of approximately three per cent (3%) of the mean aerodynamic chord, making it diflicult to practically utilize these wing sections, except where the variation in useful load limits the range of the center of gravity to approximately three per cent (3%) of the mean aerodynamic chord.

With such wings having a substantial positive Cmo moment, that is, such a moment having a value in the range from +.020 to +.045, there is available a, smaller degree of controllability within the flight range due to the larger inherently stabilizing moments. Nevertheless, it is a fact that in order to maintain stability in the flight range, the location of the center of gravity is limited to a range approximately six per cent (6%) of the mean aerodynamic chord, making it possible to practically utilize these wing sections where the variation in the useful load limits the range of the center of gravity to approximately six per cent (6%) of the mean aerodye namic chord.

Such wings having a large positive Cmo moment, that is, such a moment having a value in the range from .045 upwards, there is available a very much smaller degree of controllability is rotated by the sprocket and chain mechanism.

within the flight range due to the much larger inherent stabilizing moments. Nevertheless, it is a fact that in order to maintain controllability in the flight range the location of the center of gravity is limited to a range of approximately three per cent (3%) of the mean aerodynamic chord, making it dimcult to practically utilize these wing sections except where the variation in useful load limits the range of the center of gravity to approximately three per cent (3%) of the mean aerodynamic chord.

Therefore, a feature and characteristic of my present invention is in the discovery that the wing having such characteristics and range of center of gravity location may be employed with and as an element of a tailless airplane to obtain certain important and highly advantageous results from the standpoint of flight control and of structural design and weight distribution. Therefore, as a preferred condition, I utilize an inherently stable wing having a substantial or appreciable positive Cmc moment, for example, such a moment having a value in the range from .020 to .045 permitting a range of center of gravity location of approximately six per cent (6%) or from fifteen (15) to twenty-one (21) per cent, measured along the mean aerodynamic chord of the wing from the leading edge thereof.

In Fig. 8 of the drawings, another form and arrangement of longitudinal control is disclosed employing the basic principles of the longitudinal control in the form of Fig. 7, but, mounting the longitudinal control surfaces on fixed structure of the wings or lifting surface instead of on the neutralizing surfaces.

Referring to Fig. 8, the longitudinal control surfaces L' are mounted upon the opposite wings RW and LW as vertically displaceable trailing portions of the wing extending along the span thereof inboard of the opposite wing ailerons A, these longitudinal control surfaces L being hinged to the fixed portion of the wings forward thereof along the hinge lines 2|".

The longitudinal control surfaces L of Fig. 8 are actuated by generally similar pilot operated mechanism such as that shown and described in connection with Fig. '7, which mechanism includes the bell crank 39 connected with the control stick by the link 40 and with the opposite wing mounted bell cranks 31 and 38, respectively, by the push-pull rods 39a and 39b. Bell crank 3'! of wing RW is connected with the longitudinal control surface L by the link 31c and the bell crank 38 of the wing LW is connected with the longitudinal control surface L of that wing by the link 390. Thus, forward movement of the control stick C simultaneously lowers longitudinal control surface L while rearward movement of the control stick C simultaneously raises the longitudinal control surfaces.

The feature of the form and arrangement of Fig. 8 resides in the utilization of the opposite wing ailerons A as the adverse lift neutralizing surfaces for displacement and adjustment by the pilot independently of the longitudinal control actuation of the surfaces L, and further, without interfering with the pilot actuation of these opposite wing ailerons A as roll control surfaces. In carrying out this feature, the rotatable hollow shaft 22 having the opposite rods 23 and 24 oppositely threaded axially into opposite ends thereof, as explained in connection with Fig. 7, is utilized, but, this shaft is not only rotatably mountincluding the hand operating crank 30 of Fig. 7, but due to the fact that the shaft has axial movemerit bodily through its bearings 22b, the sprocket 32 is splined or keyed onto the shaft 22 by means of a key 32a so as to permit axial movement or sliding of the shaft 22 through the sprocket 32 while providing for rotation of the shaft 22 by rotation of the sprocket.

The simultaneous vertical displacement in the same direction for adverse lift neutralizing function of the opposite ailerons or roll control surfaces A, is carried out by rotating the shaft 22 from the hand crank 30, in a direction to either draw rods 23 and 24 inwardly or force them outwardly. Rod 23 is coupled by the push-pull'rod I5 with a right-hand wing aileron A through the bell crank I1 and link Ila, while the rod 24 is coupled with the aileron A of wing LW through the push-pull rod I6, through the bell crank l8 and the link Hla.

The differential displacement of the opposite ailerons A for roll control has been hereinbefore generally referred to and is carried out independently of the operation of ailerons A as adverse lift neutralizing surfaces through the medium of the push-pull rods 15 and I9 and the shaft 22. In the particular example hereof, the torque tube shaft l4 which is rockable or rotatable by lateral movement of the control stick C through the linkage 4|, extends to a point disposed transversely of but adjacent shaft 22 and carries a yoke 42 through which shaft 22 extends. A sleeve 43 is rotatably mounted on shaft 22 and confined between the opposite end collars 44 fixed to shaft 22. This sleeve 43 carries the diametrically Opposite outwardly extending studs 45 which are pivotally received in slots in the opposite upwardly extended arms of yoke 42. Thus, shaft 22 is free to rotate in sleeve 43 and is axially or longitudinally movable by rocking yoke 42.

Lateral control actuation of the opposite ailerment of shaft 22 is carried out by sliding this shaft in its bearings 22b and through the sprocket 32 keyed to the shaft.

In another form of longitudinal control of the invention, the longitudinal control surfaces andthe'adverse lift neutralizing surfaces are simultaneously and coincidentally but differentially operated throughout the control range from a 4 common control, which, in the example hereof,

ed in its bearings 22b but is also axially movable is provided by the pilot's control stick C. A possible arrangement of mechanism for carrying out such coincidental and differential operation of the longitudinal control and the neutralizing sur faces, is illustrated by Fig. 9 of the drawings when considered in connection with Fig. 7.

The arrangement of the system and mechanism of Fig. 9 provides for fore and aft or forward and rear swinging of the control stick C, rotating a shaft 46 which carries a relatively large sprocket or gear 41 operatively connected with a relatively small sprocket or gear 48 mounted on the shaft 29 by a chain 49. The ratio between sprocket or gear 41 on shaft 46 and the sprocket or gear 48 on shaft 29 is relatively large, so that a small degree of rotation of sprocket or gear 41 will result in considerably greater rotation of sprocket or gear 48 on the shaft 29.

Rotation of the shaft 29 through the abovearrangement of gearing rotates the shaft 22 to simultaneously raise or lower the neutralizing surfaces V, referring now to Fig. 7 of the drawings, and as this 1owering or raising of surfaces V is caused by rearward or forward movements of the control stick C, there is coincidental and simultaneous upward or downward displacement of the longitudinal control surfaces L respectively.

The cranks and connecting links and their relative angular displacements in the longitudinal control operating mechanism are so arranged that upon fore and aft movements of the control stick C, the neutralizing surfaces V will be displaced in the direction opposite to the direction of displacement of the control surfaces L and at varying angles of displacement relative to the angles of displacement of the surfaces L throughout the range of control displacement of these latter surfaces. This differential or varying angle ratio is such that the required neutralizing effect of surface V is obtained in accordance with the angle of attack of the wings or lifting surfaces and the direction of displacement of the longitudinal control surfaces, that is, whether this displacement is to a positive or negative angle position relative to the lifting surfaces or wings.

With the simultaneous, coincidental and differential actuation of the longitudinal control surfaces L and the neutralizing surfaces V from a common control point, it is essential that there be included some form of irreversible operating mechanism betwen the neutralizing surfaces V and the pilot's control, such as the control stick C, and in the example hereof, the irreversible mechanism is provided by the threaded rods 23 and 24 engaged in the threaded shaft 22, through the medium of which the displacement of the neutralizing surfaces is obtained.

It is to be further noted that a preferred feature of any arrangement of mechanism for carrying out the coincidental and differential operation of the longitudinal control and adverse lift neutralizing surfaces is to arrange such mechanism, as in the example of Fig. 9, taken with Fig; 7, so that the longitudinal control surfaces are directly coupled to the pilots control member, such as the stick C, rather than coupled mechanically through the irreversible mechanism in the operating system for the neutralizing surfaces, in order to obtain normal control stick force loads as to magnitude and direction. I have determined that while under certain conditions it may be desirable to operate the longitudinal control surfaces and the neutralizing surfaces coincidentally, the forces acting on the pilot's controls are reversed and it is practically necessary and essential to provide some means to either relieve the load entirely as by an irreversible control mechanism, or by the introduction of some other form of mechanism and/or aerodynamic means for reversing these forces on the pilot's control. This condition is therefore remedied by the foregoing feature of my invention as typified by the example of an arrangement of Fig. 9 utilizing the irreversible mecha- The invention also includes in combination with the longitudinal control surfaces of a tailless airplane, the use of aerodynamic means or members in the form of trailing surfaces or tabs mounted on a control surface and angularly vertically adjustable relative thereto. For instance,

in Fig. 1 of the drawings, I have shown trailing surfaces or trimming tabs 1 adjustably mounted on the trailing portion, of each control surface L and vertically angularly adjustable relative to the control surface on which mounted. Similar tabs are to be used with longitudinal control surfaces L of Fig. 8, if desired.

Longitudinal control of the tailless type of airplane such as provided by a design of the present'example may be obtained by the use of wingmounted, vertically disposed surfaces which are laterally displaceable, instead of by the use of the horizontal or elevator type of control surfaces L or L hereinbefore described. For example, in Fig. 20 of the drawings, I have more or less diagrammatically disclosed a longitudinal control system arrangement embodying such vertical laterally displaceable longitudinal control surfaces mounted on the opposite wings ad'- jacent the respective wing tips above and below the wing for simultaneous, lateral displacement of the surfaces above the wing to develop stalling moments, or simultaneous lateral displacement of the surfaces below the wing, to develop diving moments.

In the arrangement of Fig. 20, a vertical longitudinal control surface L is mounted on the lifting surface at the upper side thereof adjacent each tip of such lifting surface or wing and these opposite wing tip surfaces L are laterally swingable about vertically disposed axes. Suitable operating mechanism connects these two control surfaces with the pilots control stick, such as the control stick C, so that these surfaces are simultaneously laterally displaced in opposite directions when the control stick is moved rearwardly from its neutral control position, but remain inactive when the control stick is moved forward from its neutral control position. This lateral displacement of these opposite wing tip vertical surfaces develops stalling moments for longitudinal control.

A- generally similar pair of vertically disposed laterally displaceable longitudinal control surfaces L: are mounted on the lift surface or opposite wings adjacent the tips thereof, respectively, but at the under side of the lifting surface with the surfaces LF depending or extending downwardly therebelow and mounted for lateral displacement. Suitable operating mechanism is provided coupling these lower longitudina1 control surfaces L with the pilot's control stick, in such a manner that forward movement of the control stick from its normal neutral control position will simultaneously laterally displace the surfaces L in opposite directions to develop diving moments for longitudinally controlling the airplane. The operating mechanism for the lower longitudinal control surfaces LP is so arranged that upon rearward movements of the control stick C from its normal neutral control position, the longitudinal control surfaces L remain inactive and in their neutral positions.

As an example, an operating mechanism for the upper-longitudinal control surfaces I. may embody a cable 96 connected to the lower end of the control stick 0 below the axis of fore and aft swing of the stick, which cable is coupled to branch cables 96a and 86b extending over suitable pulleys outwardly along opposite wings, respectively to the operating arms 96c and 96d of the opposite vertical control surfaces U. A cable slack take up unit M is included in the cable system between the cable 98 and the branch cables 96a and 96b. 'I'hus, rearward swinging of the control stick will draw cable as forward. and simultaneously laterally displace the upper longitudinal control surfaces IF. Suitable trailing edge tabs 86c may be employed for returning the surfaces L to their normal neutral control positions upon release of the operating cables by forward movement of the control stick C, or, the surfaces may be spring loaded for return movement thereof upon release. I

The lower vertical longitudinal control surfaces L are actuated by forward movement of the control stick C through a. cable 91 connected to the control stick above its axis of longitudinal swing, which cable is connected through the slack take up unit M with the branch cables 9T0. and 91!; extending around suitable pulleys outwardly through the opposite wings to the control surface operating arms 970 and 9111, respectively, of the opposite surfaces IF. Thus, forward movements of the control stick'C draw cable 91 forwardly, and through cables 97a and 91b, the lower vertical surfaces L are simultaneously displaced laterally to develop diving moments for longitudinal control. The vertical longitudinal control surfaces L may be returned upon release to their normal neutral control positions by trailing edge tabs such as 96c or they may be spring loaded by a spring such as indicated at 98 on the right-hand control surface. Such a return spring may be connected with the control surface operating arm or in any other suitable manner. Preferably, suitable stops are provided (not shown) such as those provided for the vertical and laterally displaceable surfaces ,R or D of Figs. 10 and 11.

The cable slack take up units M in the cable systems functions to eliminate slack in that system remaining inactive when the other system is operated for control.

Such an arrangement of vertical wing mounted and laterally displaceable surfaces may be employed alone as the sole longitudinal control for the airplane, or, may be utilized together with the longitudinal control forms of Figs. '7 and 8 in which vertically displaceable horizontal surfaces, such as L and L are employed so that these vertical types of longitudinal control surfaces augment the longitudinal control moments developed by control surfaces such as L and L.

Similarly, these vertical laterally displaceable forms of longitudinal control surfaces may, in accordance with my invention, be used in cooperation with longitudinal control surfaces of the type of L or L, in arrangements by which either the vertical longitudinal surfaces L above the wing are alone utilized; or, vertically laterally displaceable longitudinal control surfaces L below the wing are alone used.

In the operating or use technique, the vertical or laterally displaceable surfaces L and L may be employed for developing the pitching moments while control surfaces of the horizontally disposed vertically displaceable type such as L, or such as the ailerons A, may be employed as ad'- verse force neutralizing surfaces. In the operation of these vertical types of longitudinal control surfaces L and L adverse forces are set up by their operation, of the same general character as discussed in connection with the adverse lift developed by the horizontal vertically displaceable types of control surfaces, so that the invention recognizes such conditions and includes with the vertical types the use of an adverse force or lift neutralizing surface or surfaces.

While I recognize that the wing tip location is the most eihcacious, my invention is not limited or restricted to such location but includes various locations spanwise of the wing. As an example of the approximately extreme inboard location of such surfaces, reference is made to the air brake sm'faces D of Fig. 11, and to the fact that such surfaces so located develop a pitching moment.

Control synchronizing v As shown in dotted outline in Fig. 1 of the drawings, the space or gap between the vertically angularly displaceable types of control surfaces such as the control surfaces L, V and A, may be closed against pressure leakage by applying suitable sealing means, such as the tapes or flexible sealing strips 95, to close the passage. Sealing of the gap between these surfaces increases the ef-- fectiveness of the controls, and in accordance with my invention, varying the degree to which the gaps are sealed is varied so as to result in a synchronizing of the control reaction on the pilot, so that, the movement of the control member actuated by the pilot is in the proper proportion with regard to both the magnitude of the force and the angular displacement of the control member, in this way synchronizing the control reaction on the pilot.

Directional or yaw control The directional or yaw control for the tailless airplane of my design is in this instance provided by vertical rudders R mounted at the upper sides 'of the wings RW and LW adjacent the wing tips, respectively, and located on the rear or trailing portions of the wings.

Referring now to Fig.. 10 of the drawings in particular, each rudder R is rotatably mounted upon shaft 50 on the wing adjacent the wing tip and so located that the trailing edge of the upwardly extending rudder R terminates substantially at or but a relatively short distance to the rear of the trailing edge of the wing tip structure. In normal neutral control position, each rudder R is disposed at substantially a ninety degree (90) angular position relative to the major longitudinal axis of the wing and is moved for directional 'or yaw control about the axis provided by the shaft 50 by displacing the rudder outwardly so that it assumes the dotted line position of the rudder R on wing RW of Fig. 10.

The operating control mechanism for each rudder R includes the outwardly extended horizontally disposed lever arm 5| in fixed relation to a rudder R for swinging therewith, and this arm, in the normal n'eutral control position of a rudder R is engaged against a stop member 52. A spring 53 is connected between the free end of each rudder actuating arm 5! and a fixed point in the wing structure to the rear of the arm so that in each instance such spring 53 normally draws and holds the arm 5| swung rearwardly against the stop 52 to maintain the rudder R in its normal neutralcontrol position.

there maybe relative rotational movement of these shafts. It so happens that in the present example, I have shown a possible dual control pedal arrangement for side by side seats, such arrangement; including the pair of pedals 54' and 55' with pedal 54 carried by shaft 58 and pedal 55' by shaft 51. The pedal 54' of shaft 56 extends through a slot or opening provided in the shaft to permit movement of this pedal for rotation of shaft 56 independently of and without interfering with the shaft 51, as will be clear by reference to Fig. or to Fig. 12.

An arm 58 fixed on shaft 56 is connected by an operating cable I! with the outer free end of the crank arm SI of the left rudder on the win LW and an arm {I isflxed on the shaft 51 and is connected with the outer free end of the crank arm SI of the right rudder on wing RW by an embodies a cylindrical casing 62 carrying a plunger flu mounted for longitudinal reciprocation within the cylinder and extending out- 'wardhr through one end of the cylinder for connection to the cable in which the unit is mounted. The opposite end of the casing 62 is adapted to be connected by any suitable coupling to an end of the cable in which the unit is utilized.

A coil expansion spring 62b is interposed between the head of the plunger 62a and the shoulder or abutment structure He in the casing and the plunger carries a collar or stop 62d spaced a distance from the. plunger head for engaging the abutment structure 620 to limit movement of the plunger in the casing in onedirection. In normal position connected into an operatin cable, the normal load in the cable maintains the coil spring under partial contraction so that upon removal of the load in the cable, the sprin 62 expands further to force the plunger through the casing and draw the opposite sections of the cable in which the unit is mounted closer together and thus take up any slack in the cable.

With the-arrangement of opposite wing tip rudders and the operating mechanism therefor, in the form of the present example, only one rudder is operated at a time to obtain directional or yaw control. For example, if it is desired to turn the airplane to the left, the left rudder R on wing LW is displaced by the pilot laterally outwardly, while the opposite right rudder R on wing RW remains in its normal neutral position. If it is desired to turn the airplane to the right, the right rudder.R on wing RW is actuated by the pilot and the left rudder on wing Lw remains in its normal neutral control position. I

Outward displacement laterally of the left rudder R on wing LW in order to set up yawing moments acting in a direction to turn the airplane to the left, is accomplished by pushing the left pedal 54 (5.) forwardly to rock shaft 56 and pull the cable 59 forwardly and thereby swing rudder R laterally outward against the tension of its spring 53. During this left rudder actuation,- shaft 56 rotates independently of the shaft 51 and the right pedal 55 is moved in the which rocks shaft 51 and through arm I. and' cable 6 swings right rudder R laterally outwardly to control position against the tension of spring 53. Release of the right pedal II permits the spring 53 to return right rudder R to'lts normal neutral control position with its arm I held against the stop 52'.

In place of or in conjunction with the rudder return spring 53, I may employ a form of aerodynamical means for returning a rudder to and holding it in neutral position against its stop. such for example as a suitable tab surface 3dmounted on the trailing edge of the rudder and angularly adjustable to establish the required force acting in the required direction to return and maintain the rudder to and at its neutral control position.

Ifdesired or found expedient, a form of pedal shaft motion reversing mechanism of my invention may be employed for a steering control system of the type above described and as shown in Fig. 10 of the drawings. Such a reversin unit N is disclosed in operative position coupling shafts 5i and 51 in Fig. 10 of the drawings and is shown in detail by Figs. 5 and 6 of the draw- Referring now to Figs. 5 and 6, the unit N includes a suitable casing structure 63 in which is mounted a shaft 64 carrying the spaced opposite wheels or rollers S5 rotatably mounted there: on, with the rollers 65 confined in opposite tracks provided by the casing structure 63, so that this shaft and its supporting rollers are movable or slidable longitudinally back and forth within the casing structure 63. Casing structure 63 is provided with longitudinally disposed slots or openings in its upper and lower sides and a link it is mounted on shaft 64 intermediate the rollers 65 and extends forwardly therefrom to and is pivotally connected with an upwardly extending arm 61 fixed on the pedal shaft 51. A link 68 is mounted on and carried by the shaft 64 and this link 68 extends forwardly and downwardly to an arm 6! fixed on and carried by the pedal shaft 56.

Thus, the unit N operatively couples and connects the .pedal shafts 56 and 51 carrying the right and left pedals, through the medium of the links 66 and 68 and the common shaft. bodily transversely movable back and forth in the easing structure 63. Hence, upon operation of a left pedal 54 (54') to actuate the left rudder with the forward rotation of the shaft 56, arm 8! on that shaft is rocked rearwardy and through link 68 slides or rolls shaft 64 in the unit N rearwardly in the casing structure 63. Rearward movement of shaft it pulls the link Gt rearwardly and rearwardly rotates the right pedal shaft 51, thus reversing the movement of that shaft and the right pedal 55 (55') carried by that shaft with respect to the forward control operating movement of the left pedal 5t (54'). Upon the control actuation of a right pedal 55 (55') to rotate shaft '51 forwardly, the unit N reverses .of the drawings.

such motion and transmits it to shaft 56 as a rearward motion of that shaft and the left pedal 65 (54') carried by such shaft. Thus, a simultaneous operation of a pair of right and left pedals in the reverse directions is obtained. Withsuch reverse movement of the opposite idle pedal to a control operated pedal, there is of course a slackening of the rudder operating cable connected to the idle pedal but the slack so resulting in a rudder operating cable is taken up by a slack take-up unit N connected in the cable.

A rod or the like 64a is connected through .the common shaft 64 and is reciprocated by movements of the shaft longitudinally in the easing. This reciprocating rod 64a may be extended through any suitable mechanism for steering actuation of the link rod 85 of the wheel steering mechanism of Fig 12, or may be utilized for actuating the rudder operating cables or rods of the rudder control mechanism of Fig. 10.

It is to be lparticularly. noted that the opposite wing tip rudders R providing the directional or yaw control in accordance with my invention, have no associated fixed vertical fin area forming portions of the directional control surfaces. In

normal neutral control positions held by the springs 53 or tabs 53a, the opposite wing tip rudders R function as vertical fins and, upon directional control operation of either of these rudders, the opposite rudder is not actuated but remains in its normal neutral control position and continues tofunction as vertical fin area. In connection with the opposite wing tip rudders R of the invention, a feature thereof resides in utilizing for each rudder a surface having a cambered section in which the cambered side, or side of greatest camber, is on the inner side of the rudder, as will be clear by reference to Fig. 1

Such arrangement which provides the rudder surfaces with their inboard sides cambered obtains an increase in control moment due to the rearward location of the center of pressure on a surface of this kind at small angles, of lateral displacement. In the directional control operation of the opposite wing tip rudders R so designed, mounted and arranged, the displacement of a rudder R results primarily in establishing drag as well as a stalling moment at its wing tip.

The opposite vertical laterally displaceable rudder forming surfaces R may; if desired, be used for simultaneous outward or inward displacement for the purpose of creating drag so that these wing tip surfaces may then be utilized as air brakes or surfaces for creating a stalling moment, and my invention includes the operation and use of such wing tip surfaces for this purpose to carry out such air brake or stalling function. Any suitable mechanism may be employed for simultaneously outwardly or inwardly swinging these surfaces, such, for example, as the mechanism shown in Fig. 11 of the drawings and described hereinafter.

While in the preferred form, the rudders R are located at the upper side of the wings, my invention recognizes and includes locations of the rudders both above and below the wings, such as described in connection with the use of such vertical surfaces for longitudinal control.

It is recognized that under certain design conditions, a relatively large cross-wind force is introduced when the rudders are turned outboard, and that this cross wind force may be detrimental to the directional'control of the aircraft. Therefore, my present invention contemplates and includes that under such conditions, the tip rudders may be interconnected with the air brakes or drag establishing surfaces so as to neutralize this cross wind force, or, as another 1 alternative, that the tip rudders may be turned inboard in order to reverse the direction of the cross wind force. My invention further includes in its treatment of this condition, the use of multi-plane tip rudders actuated in' opposite directions for the purpose of neutralizing the cross wind force.

A feature of the invention is based upon the fact that in aircraft that have small directional stability, as in the case of the tailless types, the dihedralangle of the wing has a material effect upon the directional stability, and that where the dihedral angle is smalL-the directional stability of the complete aircraft is thereby improved, and that where the dihedral angle is large, the directional stability at increasing angles of attack will be lessened and may, in fact, result in instability under certain conditions. Therefore, in accordance with a feature of my present invention, the

dihedral angle of the wing is maintained at A further characteristic of the invention recognizes that a directional or yaw control is possible in a tailless design of my type by the elimination of the movement of the vertical surfaces. A substitution for this movement is obtained by displacing the aileron or roll control'surfaces to establish drag at their respective wing tips, thus causing a change in direction as well as introducing their primary function of roll control. This dual function requires that the ailerons themselves be readjusted in relation to their angle of trail to the fixed portion of the wing. By this adjustment, the adverse drag is eliminated or reduced to a degree that permits the directional or yaw control of the airplane.

In accordance with another feature and form of two-control arrangement, the invention provides the elimination of the movement of the ailerons or roll control surfaces A, and obtains roll control by the differential operation of the yaw control surfaces or rudders R, in the form of Fig, 10. Thus, two controls embodying the pitch control by surfaces L or L and roll and yaw control by rudders B, may be provided.

Air brakes The development of drag for the purpose of braking or retarding forward movement of the airplane forms a phase of my present invention and I have disclosed herein an arrangementof movable surfaces for developing drag for braking purposes, and in addition, I have so located and arranged these surfaces relative to the body B of the airplane and the propeller P that a beneficial cooperation with the airflow past the body and to the propeller P is obtained.

Referring now particularly to Figs. 1 and 2 of the drawings, I have shown a possible embodiment of drag establishing surfaces D in the form of vertical surfaces mounted at the upper side of the trailing portion of the lifting surface at opposite sides of the reai or trailing portion of the body B. In the specific example hereof, these surfaces are mounted at the trailing portions of the opposite wing root forming portions LW' and RW' of the center section of the lifting surface, and are located spaced equidistant from the long tudinal axis of the body B and from each other 

